The present invention relates to a shared interface device, especially to a shared interface device connected between a portable electronic device and a peripheral unit.
The current portable electronic devices such as personal digital assistants (PDA) and cellulous phones are often connected to peripheral unit such as keyboard for inputting data. In those portable electronic devices, the power transmission function and the signal transmission function are generally assigned at different pins.
As shown in FIG. 1, conflict is occurred if the power transmission function and the signal transmission function are assigned at the same pin 8 of a portable electronic device 1a. When a peripheral unit 2a is connected to the portable electronic device 1a and powered by the portable electronic device 1a through the pin 8 of the portable electronic device 1a, the peripheral unit 2a can only send data to the portable electronic device 1a and cannot receive data from the portable electronic device 1a because the transmitting data pin and the power supplying pin of the portable electronic device 1a are defined at the same pin 8. Therefore, the peripheral unit 2a cannot communicate with the portable electronic device 1a in bidirectional fashion.
Moreover, if the pin 8 of the portable electronic device 1a is functioned to transmit data to the peripheral unit 2a, the peripheral unit 2a cannot be powered by the portable electronic device 1a. This is inconvenient for user.
It is the object of the present invention to provide a shared interface device connected between a portable electronic device and a peripheral unit, wherein both the power supplying function and the data transmission function can be assigned to one pin with no confliction and bi-directional data transmission is possible.
To achieve the above object, the present invention provides a shared interface device having a switch and an energy-storing element and arranged between a portable electronic device and a peripheral unit. When a Txc3x97D/POWER pin of the portable electronic device is HI and there is no transmitted data, the switch is ON to provide electric power to the peripheral unit and charge the energy-storing element. Moreover, when there is transmitted data present and the Txc3x97D/POWER pin of the portable electronic device is LO, the switch is OFF and the energy-storing element is functioned as backup power supply of the peripheral unit. Moreover, when there is transmitted data present and the Txc3x97D/POWER pin of the portable electronic device is HI, the switch is ON to provide electric power to the peripheral unit and charge the energy-storing element.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing, in which: